Chapter 25: assessment of the respiratory system Flashcards
Primary purpose of respiratory system
Gas exchange: transfer of O2 and CO2 bt atmosphere and blood
Upper respiratory tract
nose, mouth, pharynx, epiglottis, larynx, trachea
Turbinates
increase surface area of nasal mucosa which warms and moistens air as it enters the nose
Larynx
covered by epiglottis during swallowing
houses vocal cords
Trachea
-Carina
10-12 cm long
covered with U-shaped cartilage to allow swallowing
bifurcates at carina at angle of Louis at 4th and 5th vertebrae
Carina is super sensitive –> stimulation of it triggers intense coughing
Lower Respiratory tract
Bronchi
Bronchioles
Alveolar ducts
Alveoli
Lungs
-where is aspiration more likely to happen?
R = 3 lobes
L = 2 lobes
Mainstem bronchi, pulmonary vessels, and nerves enter at hilus
Right bc mainstem bronchi is straighter, shorter, and wider
Functional roles of each part of the lower airways
Trachea and bronchi = anatomic dead space (VD); no gas exchange
Bronchioles = smooth muscle constricts and dilates
Alveoli = terminal part of respiratory tract; gas exchange
Tidal volume and what part of that is dead space?
Tidal volume is about 500 mL
Of that, 150 mL is dead space
Alveoli: structure and function
main site of gas exchange with pulmonary capillaries
300 mil- each .3mm across
Connected by pores of Kohn –> let air pass, but also bacteria
Volume of 2500 mL
Surface area of a tennis court
Surfactant
lipoprotein secreted by alveoli when stretched
-reduces surface tension, making alveoli less likely to collapse
People take slightly larger breath (sigh) every 5-6 breaths to promote surfactant secretion
Atelectasis
collapsed alveoli
Big risk for post-op because anesthesia, decreased mobility, and pain alter breathing
In ARDS, lack of surfactant causes widespread atelectasis and collapse of lung tissue
Blood supply: Pulmonary circulation and Bronchial circulation
Pulmonary
-pulmonary artery brings deoxygenated blood to lungs from R ventricle
-gas exchange happens in capillaries
-pulmonary vein brings oxygenated blood to left atrium
Bronchial
-bronchial arteries branch off of thoracic aorta
-azygos vein brings deoxygenated blood to superior vena cava
Chest wall components
Thoracic cage
-12 pairs of ribs and sternum –> protect lungs and heart
Mediastinum
-space in middle of thoracic cavity
-houses heart, aorta, and esophagus
-separates R and L lungs into 2 separate compartments
Pleura
-visceral has no pain fibers/nerve endings, but parietal does –> that’s why inflammation can cause pain with breathing
-intrapleural space –> 20-25 mL fluid to lubricate during breathing and promote expansion of lungs during inspiration
Diaphragm
-major muscle of respiration
-innervated by R and L phrenic nerves from cervical vertebrae 3-5
-each side innervates one half (hemidiaphragm)
-damage above C3 paralyses entire diaphragm
Issues with intrapleural space
-usually fluid drains via lymphatic circulation
Pleural effuision = accumulation of fluid here
-can happen bc blockage of lymphatic drainage from cancer
-can happen bc of hear failure, causing imbalance bt intervascular and oncotic fluid pressure
Emphysema
-purulant pleural fluid with bacterial infection
Muscles during inspiration
Diaphragm: contracts and moves down
Internal intercostals: relax
External intercostals: contract
scalene: contract to raise ribs 1 and 2
Oxygenation
-normal partial pressure
-normal arterial saturation
Oxygenation = O2 from atmosphere to organs and tissues
-oxygen dissolved in plasma = partial pressure of oxygen in arterial blood (80-100)
-Oxygen bound to hemoglobin = arterial oxygen saturation (SaO2) –> (>95%)
O2 and CO2 move via diffusion until equilibrium is reached
Ventilation
-inspiration and expiration due to intrathoracic pressure changes and muscle action
-gas flows from higher pressure to lower pressure
Inspiration takes effort- expiration is passive
-elastic recoil = lungs bounce back after being stretched –> elastin in alveolar walls and around bronchioles
Ventilation issues
Dyspnea
-mandates that accessory muscles help expand thorax
Shallow breaths
-caused by phrenic nerve paralysis, rib fractures, neuromuscular issues
-lungs don’t fully inflate and gas exchange is impaired
Active expiration
-caused by exacerbations of asthma or COPD
-abs, intercostals, scalenes, and trapezius engaged
Compliance and Resistance
Compliance
-ease of lung expansion –> elasticity of lungs and elastic recoil of chest wall
-Decrease = hard to inflate; Increase = hard to recoil
-Decrease caused by fluid (pulmonary edema, ARDS, pneumonia); less lung elasticity (pulmonary fibrosis, sarcoidosis); or restriction of lung movement (pleural effusion)
-Increase caused by destruction of alveolar walls and less tissue elasticit (COPD)
Resistance
-airflow impeded during inspiration and/or expiration –> altered airway diameter
-asthma causes bronchoconstriction
-secretions are also an issue
Respiratory center
Medulla in brainstem
responds to chem and mech signals
sends impulses from spinal cord and phrenic nerve to respiratory muscles
Central Chemoreceptors
responds to changes in PaCO2 and pH in surrounding fluid
Central chemoreceptors in medulla
-increase H+ concentration = acidosis –> results in increased RR and VT (tidal v)
-decrease H = alkalosis –> decreased RR and VT
Increased PaCO2 = increased H2CO3 = decreased pH of CSF –> increased RR
Decreased Pa CO2 = decreased H2CO3 = increase pH of CSF –> decrease RR
Peripheral chemoreceptors
in carotid bodies and aortic bodies
-respond to decreased PaO2, decreased pH, and increased PaCO2
-stimulates respiratory center to increase RR
COPD - chronically increased PaCO2 –> desensitizes person to further increases
-maintain ventilation from hypoxic drive
-healthy person’s PaCO2 doesnt vary more than 3 mm Hg
Mechanical receptors
in conducting upper airway, chest walls, diaphragm, and alveolar capillaries
Stimulated by:
-irritants (conducting airway) –> stimulates cough
-stretch (smooth muscle) –> Hering Breuer reflex stops overdistension of lungs
-J receptors (alveolar capillaries) –> sense high pulmonary capillary pressure causing rapid shallow respiration seen in pulmonary edema